Jennifer Stamps, a graduate student in the McKnight Brain Institute Center for Smell and Taste, came up with the idea of using peanut butter to test for smell sensitivity. when she was working with Kenneth Heilman MD, a professor of neurology at the University of Florida.
One of the first places in the brain to degenerate in people with Alzheimer’s disease is the front part of the temporal lobe that evolved from the smell system. This portion of the brain is also involved in forming new memories. The ability to smell is associated with the first cranial nerve – the olfactory nerve.
Because peanut butter is a “pure odorant,” it is only detected by the olfactory nerve.
In a small pilot study, patients sat down with a clinician, a tablespoon of peanut butter and a metric ruler.
The patient closed his or her eyes and mouth and blocked one nostril. The clinician opened the peanut butter container and held the ruler next to the open nostril while the patient breathed normally. The clinician then moved the peanut butter up the ruler one centimeter at a time during the patient’s exhale until the person could detect an odor.
The distance was recorded and the procedure repeated on the other nostril after a 90-second delay.
The clinicians running the test did not know the patients’ diagnoses, which were not usually confirmed until weeks after the initial clinical testing.
Patients in the early stages of Alzheimer’s disease had a dramatic difference in detecting odor between the left and right nostril – their left nostril did not detect the smell until it was an average of 10 centimeters (almost 4 inches) closer to the nose than the right nostril.
This was not the case in patients with other kinds of dementia. These patients had either no differences in odor detection between nostrils or the right nostril was worse at detecting odor than the left one.
Of the 24 patients tested who had mild cognitive impairment, which sometimes signals Alzheimer’s disease and sometimes turns out to be something else, about 10 patients showed a left nostril impairment and 14 patients did not. The researchers said more studies must be conducted to fully understand the implications.
“At the moment, we can use this test to confirm diagnosis,” Stamps says. “But we plan to study patients with mild cognitive impairment to see if this test might be used to predict which patients are going to get Alzheimer’s disease.”
Many of the tests used to confirm a diagnosis of Alzheimer’s disease or other dementias can be time-consuming, costly, or invasive. In contrast, according to the researchers their peanut butter and ruler test could be used by clinics that don’t have access to the personnel or equipment to run other, more elaborate tests required for a specific diagnosis.
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